It is widely known that various organometallic compounds and asphaltenes are present in petroleum crude oils and other heavy hydrocarbon streams, such as petroleum hydrocarbon residua, hydrocarbon streams derived from tar sands, and hydrocarbon streams derived from coals. The most common metals found in such hydrocarbon streams are nickel, vanadium, and iron. Such metals are very harmful to various petroleum refining operations, such as hydrocracking, hydrodesulfurization, and catalytic cracking. The metals and asphaltenes cause interstitial plugging of the catalyst bed and reduced catalyst life. The various metal deposits on a catalyst tend to poison or deactivate the catalyst. Moreover, the asphaltenes tend to reduce the susceptibility of the hydrocarbons to desulfurization. If a catalyst, such as a desulfurization catalyst or a fluidized cracking catalyst, is exposed to a hydrocarbon fraction that contains metals and asphaltenes, the catalyst will become deactivated rapidly and will be subject to premature removal from the particular reactor and replacement by new catalyst.
Various materials have been employed in the treatment of petroleum hydrocarbon streams for the removal or substantial reduction of the metals, as well as asphaltenes, contained therein. For example, such treatment may have been conducted with bauxite (U.S. Pat. No. 2,687,985 and 2,769,758); a material consisting essentially of titania and alumina (U.S. Pat. No. 2,730,487); a material consisting essentially of iron oxide and alumina (U.S. Pat. No. 2,764,525); fresh or spent bauxite, activated carbon, artificial and synthetic clays, and silica-alumina materials (U.S. Pat. No. 2,771,401); and a porous alumina having extensive macroporosity, the latter being in an ebullated bed (U.S. Pat. No. 3,901,792).
Hydrogenation, hydrodesulfurization, hydrodenitrogenation, and/or demetallization catalysts containing at least one metal from Group VI of the Periodic Table of Elements and at least one metal from Group VIII of the Periodic Table of Elements on a solid porous refractory inorganic oxide material are known (U.S. Pat. Nos. 3,649,526; 3,668,116; 3,814,683; 3,876,680; 3,114,701; and 3,960,712). In some cases, the catalyst may be a large-pore, high-surface area catalyst (U.S. Pat. Nos. 3,730,879; 3,684,688; 3,393,148; 3,898,155; and 3,902,991). There are also disclosed catalysts which may have one or more metals from Group VI and Group VIII of the Periodic Table of Elements on a support, such as alumina (U.S. Pat. Nos. 3,297,588; 3,712,861; 3,891,541; and 3,931,052). In addition, catalysts containing one or more metals from Group VI and Group VIII on a support, such as alumina, and having large pores and a high surface area have been disclosed (U.S. Pat. Nos. 3,876,523; 3,928,176; 3,977,961; 3,985,684; 3,989,645; 3,993,598; 3,993,599; and 3,993,601). However, not one of the references teaching these latter catalysts discloses that only a small amount of the hydrogenation metal is to be used. The catalyst may contain from about 5 to about 50 wt.% Group VI metal and about 1 to about 12 wt.%, preferably, about 4 to about 8 wt.% Group VIII metal. No actual examples of catalysts containing only one metal and having that metal present in an amount of less than 4 wt.% were presented.
In addition, there has been disclosed in a vague manner a hydrodesulfurization catalyst containing at least 4 wt.%, preferably 8 to 25 wt.%, based on the total catalyst and calculated as the metal, of a Group VI component and an alumina gel. The catalyst may have large pores and a high surface area and may also contain from 1 to 10 wt.% of a Group VIII component, based on the total catalyst weight and calculated as the metal. If only one hydrogenation metal is present, it must be present in an amount of at least 4 wt.%, calculated as the metal. None of the catalysts in the examples contained only one metal. Furthermore, the catalyst is not considered for demetallization (U.S. Pat. No. 3,577,353).
There has now been found and developed a catalyst that is suitable for the hydrodemetallization of hydrocarbon streams, which catalyst contains only one hydrogenation metal in a relatively small amount deposed on a large-pore alumina. The catalyst has special physical characteristics.